3-hydroxypropionic acid (3-HP) is a three carbon carboxylic acid identified by the U.S. Department of Energy as one of the top 12 high-potential building block chemicals that can be made by fermentation. Alternative names for 3-HP, which is an isomer of lactic (2-hydroxypropionic) acid, include ethylene lactic acid and 3-hydroxypropionate. 3-HP is an attractive renewable platform chemical, with 100% theoretical yield from glucose, multiple functional groups that allow it to participate in a variety of chemical reactions, and low toxicity. 3-HP can be used as a substrate to form several commodity chemicals, such as 1,3-propanediol, malonic acid, acrylamide, and acrylic acid. Acrylic acid is a large-volume chemical (>7 billion lbs/year) used to make acrylate esters and superabsorbent polymers, and is currently derived from catalytic oxidation of propylene. Fermentative production of 3-HP would provide a sustainable alternative to petrochemicals as the feedstock for these commercially-significant chemicals, thus reducing energy consumption, dependence on foreign oil supplies, and the production of greenhouse gases.
Unlike lactic acid, 3-HP is not a major end product of any pathway known in nature, being found in only trace amounts in some bacteria and fungi. Thus, a greater deal of genetic engineering is necessary to generate yeast that produce 3-HP. Several metabolic routes have been described to produce 3-HP (see WO01/16346; WO02/042418; WO2012/074818). However, there is still a need in the art to further improve 3-HP production in a more cost-effective manner on an industrial scale. In particular, there is a need to improve 3-HP production yields by minimizing the formation of unwanted byproducts.